Dust shield



' secured to the body .of the microscope.

prisms and lenses.

Patented Aug. 20, 1946 -Bausch & LoinbOpticaL Company,

Rochester,

N. Y" a corporation of New York Application February 26 1944,.SerialNo. 524,030

1 This invention relates to optical instruments and moreparticularly to a dust shield for microscopes, telescopes, and the like. ""In the use of microscopes, it is common practice to employ several eyepieces forsecuring different"magnificationsfof the. image of the object an'dyforthis purpose, the eyepieces can be interchangeably mounted in the eyepiece tubes In prismatic microscopes, the end of each tube is generally mounted in the body of the microscope in 's'pace'd'relation to the exit "face of one of the prisms of the prism system. Upon removal and replacement'of theeyepieces, dust in the air surrounding theexterior end of the eyepiece tube "enters the tube and lodges on the prisms and objective;

'This dustis a source/of annoyance to the microscopist for the dust castsshadows in -the image fieldan'd reduces illuminati'on'of the image when lodged onfthe. transmittingfaces of the Oil' particles are particularly objectionable if they adhere to the reflecting faces of the prisms for such particles often distort the image due to the differences in the indices of refraction of the oil and the glass of the prism.

To remove the dust, the microscope must be taken apart and the dust brushed from the prisms and objective. In most cases, the disassembling and reassembling of the microscope requires a factory operation for the exactitude with which the optical elements must be necessarily held in the optical axis of the instrument requires a skilled workman to perform this operation or elsethe optical elements may be moved out of their optical alignment and the utility of the instrument be materially impaired. Whether or not this operation be performed by a skilled workman or the microscopist, the elimination of the dust from the instrument is a tedious and pa nstaking task due to the tendency of the dust to settle back on the cleaned surfaces of the optical elements of the microscope.

It is the principal object of the present invention to provide in a microscope or the like, a shield which effectively prevents the entrance of dust into the body of the instrument through the eyepiece tube. To accomplish the result desired, the interior end of the eyepiece tube adjacent the exit face of one of the prisms telescopically receives a tube of such a length that a gasket of rubber, or other resilient material carried by the end face thereof engages the exit face of the prism. As the gasket is held tightly against the face of the prism by the frictional engagement eyepiece tube the prism.

,ment, and combination of parts as will hereinafter he more fully set forth and pointed out. as

the specification proceeds.

Inthe drawing: I

Fig. 'l 'is' a perspective view of a vertical section of one body unit of a binocular microscope'having a dust shield embodying my invention.

Fig. 2 is a fragmentary sectional View showing the "dust shield carried by thelower' end of the and engaging the upper portion'of {Referring to the drawing, it will be seenthat the invention is there shown, for the purposes of illustration only, as being embodied in'a body unit of a binocular microscope of the Greenough type, designated generally at Hi. It will be seen that generally speaking, the microscope comprises a casing or housing I l inwhich is mounted a prismatic reversing system comprising a pair of prisms l2 and IS. The bottom wall I4 of the casing is formed with a downwardly extending annular flange [5 into which is threaded the objective tube I 6 carrying an objective IT. The other end of the casing II is closed by a cap l8 having a threaded opening receiving one end of an eyepiece tube IS. The eyepiece tube is securely held in the cap [8 by threading the tube into the opening in the cap until the flange 2| of the tube is firmly seated upon the edge surface defining the opening in the cap.

In prismatic instruments, such as binocular microscopes of the type shown, the prism assembly is often carried within a casing such as shown at H in spaced relation to the eyepiece tube. In the interchange of eyepieces to effect different magnifications of the object and also in the use of the microscope, dust and oil particles frequently enter the eyepiece tube and pass therethrough into the casing to lodge on the prism transmitting and reflecting faces and also on the back surface of the objective. Dust on the transmitting faces casts shadows in the image field and reduces illumination of the image while oil particles often adhere to the reflecting faces of the prism causing distortion of the image due to scribes an annular area on gasket is seated upon the the variation in the indices of refraction of the oil and the glass of the prism.

end of the member 22 adjacent the prism I2 is" for-med with a flange 23 underlying the endof;

- the eyepiece tube 19, The

From the foregoing, it will be apparent that I am able to attain the objects of my invention l ited thereto forthe shield may be used in any -'optical instrument wherem an optical element is bottom surface of the fiange 23 is formed with a eircumferential 'groove adapted to receive an annular gasket 25 of rubber, or like elastic material, 7 whichfwhile firmly'seated in-the groove, extends outwardly therefrom to engage the transmitting face 26 of the prism l2. against the face 26 of the prism l2 bythe frictional engagement of the tubular member 22 with the eyepiece tube l9 v v .It will be apparent that thegasket 25 circumthe face 26v of the .prism l2 and, by so doing, eflectually seals the interior of the casing from dust passing into the eyepiece tube. The dust willthusj be localized on the face of fined by the opening in the gasketand'may be readily removed from the face of the prism through the eyepiece tube in any desired manner.

In theassembly of the. dust shield, with the microscope, the cap is removed'and the tubular member 22, slid over the end ofthe eyepiece tube H). The cap is thenrreplaced on the casing and then the flange 23 is pushed downwardly by any suitable toolv passe'drinto thetube l9 until the face 250i the prism l2.

As the tubular member '22 telescopically receives theeyepiece tube l9, the dust shield does not interfere with the movement of eyepieces of substantial length in the eyepiece tube. 1 Also, the opening in the flange 23 is of sumcient diameter to prevent vignetting.

The gasket 25 is held tightly the prism within the limits de-' ,mounted closely adjacent the eyepiece tube and' can be used to form *this'purpose, various modifications can be made an element of the seal. For

without; departing from the spirit of my invention as defined in the appended claims.

I claim: f v

- 1. An optical instrument having in combination a casing provided with an aperture, an op-' tical element mounted in the casing, said element having a surface spaced from and in alignment rwithrthe aperture, a lens tube mounted in said aperture and having an end: projecting. into the casing adjacent to. but out of, contact with said surface, a tubular member telescopically mounted V on said end, and gasket means carried by'said member and adapted to engage the surface'of the element whereby the passage of dust through the tube and into the casing is prevented.

2. An optical instrument comprising a casing having an aperture, an optical elementmounted within the vcasing in alignment with the aperture, a lens tube threadedly mounted on the easing and having an end extending .through the aperture and into the casing inproximity to a surface of the element, a tubular member slidably mounted on the outer surface ofthe rend of the tube, said member having an integral flange, gasket means carried on said flange, said member being adjustably positioned on the gasket means into contact with the. surface of the element whereby the passage [of dust through the tubeand into the Leasing is pre vented the tubegto bring .Y

,' JGEQ GE 3.; antigen; 2 

